Dry hazards

Shape Charge Effectiveness — ca 120% of TNT Storage — Dry Hazard Class 9> Compatibility Group I... 

Storage (for every expl) Dry hazard class (quantity - distance) 9 and compatibility group ... 

Based on the procedure developed by CIBA-Geigy [8], the material is rated from 1 to 6 depending upon its reaction to an electrically heated platinum wire. The sum of the two ratings is then taken as the overall index of the drying hazard and subsequently a hazard classification is determined (Table 56.1). Products with a hazard class Tr 3 should not be dried in heated vessels since safe handling of the dry product cannot be assumed. 

While it is necessary to provide adequate precautions to personnel when freeze-drying hazardous products, overcautious risk assessment can result in unnecessary or even impractical working regimes. An example where risk assessment may require modification is where live attenuated vaccines are freeze-dried on an industrial scale, when it may be operationally impossible to handle such strains with the precautions essential when processing virulent strains of that organism. 

Media formulated for freeze-drying hazardous products have to satisfy two quite different criteria which are ... 

The use of pressurised steam for decontaminating a freeze-drier The advantages of using pressurised steam as outlined above strictly apply only when sterilising freeze-driers prior to processing parenteral products. When it is intended to use pressurised steam to decontaminate a freeze-drier which has been used to dry hazardous materials, a potentially serious disadvantage should be considered related to the need to raise the... 

Clothing the operator completely in an impervious plastic suit represents the ultimate in personal protection and has the additional merit of isolating the product completely from operator and such suits have been used to maintain sterility during pharmaceutical manufacture. Isolator suits should not be used as the primary means of protecting the operator but must be used only in combination with effective techniques for safely dispensing, handling and freeze-drying hazardous products. 

Dust Filter. The cloth or bag dust filter is the oldest and often the most reHable of the many methods for removing dusts from an air stream. Among their advantages are high (often 99+%) collection efficiency, moderate pressure drop and power consumption, recovery of the dust in a dry and often reusable form, and no water to saturate the exhaust gases as when a wet scmbber is used. There are also numerous disadvantages maintenance for bag replacement can be expensive as well as a sometimes unpleasant task these filters are suitable only for low to moderate temperature use they cannot be used where Hquid condensation may occur they may be hazardous with combustible and explosive dusts and they are bulky, requiring considerable installation space. 

The rolling operations that foUow take place first on hot (95°C) differential-speed roUs which dry and coUoid the paste and convert it iato sheet form, and then on even-speed roUs which produce smoothly surfaced propellant sheets ia which all iagredients have been uniformly iacorporated. The roU gap ia the differeatial roUs is adjustable to produce sheets of various thicknesses, and rolling is continued until the moisture is reduced to a predetermined level, usually less than 0.5%. The sheet is then cut off the roU. Differential rolling is potentially hazardous, and fires are not uncommon, although detonations are not apt to occur. Operations are conducted by remote control. 

Solution Casting. The production of unsupported film and sheet by solution casting has generally passed from favor and is used only for special polymers not amenable to melt processes. The use of solvents was generally very hazardous because of their flammabiUty or toxic nature. The cost of recovery and disposal of solvents became prohibitive for many lower price film appHcations. The nature of the drying operations leads to problems with solvent migration and retention that are not problems with melt-processed polymers. 

The importance of hydrolysis potential, ie, whether moisture or water is present, is illustrated by the following example. In the normal dermal toxicity test, namely dry product on dry animal skin, sodium borohydride was found to be nontoxic under the classification of the Federal Hazardous Substances Act. Furthermore, it was not a skin sensitizer. But on moist skin, severe irritation and bums resulted. 

The most overlooked hazard and contaminant is water (99). Water reacts with isocyanates at room temperature to yield both ureas and large quantities of carbon dioxide. The presence of water or moisture can produce a sufficient amount of CO2 to overpressurize and mpture containers. As Httle as 30 mL of water can result in 40 L of carbon dioxide which could result in pressures of up to 300 kPa (40 psi). For these reasons, the use of dry nitrogen atmospheres is recommended during handling. If a plant air system must be used, purification equipment, such as oil traps and drying beds, should be installed between the source and the isocyanate vessel. 

Finish removers are appHed by bmshing, spraying, troweling, flowing, or soaking. Removal is by water rinse, wipe and let dry, or solvent rinse. Removers may be neutral, basic, or acidic. The viscosity can vary from water thin, to a thick spray-on, to a paste trowel-on remover. The hazard classification, such as flammable or corrosive, is assigned by the U.S. Department of Transportation (DOT) for the hazardous materials contained in the remover. 

There are explosion hazards with phthahc anhydride, both as a dust or vapor in air and as a reactant. Table 11 presents explosion hazards resulting from phthahc anhydride dust or vapor (40,41). Preventative safeguards in handling sohd phthahc anhydride have been reported (15). Water, carbon dioxide, dry chemical, or foam may be used to extinguish the burning anhydride. Mixtures of phthahc anhydride with copper oxide, sodium nitrite, or nitric acid plus sulfuric acid above 80°C explode or react violently (39). 

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